ISSUE 6
OCT-DEC 2004

Improvements in Irrigation Methods

Although agriculture in Paros Island is not the major economic activity, it is vital to the local economy and social structure. The climatic conditions on the island demand that any crops need to be irrigated, for at least part of the year; the season of highest irrigation demand coincides with the peak tourist season, creating strong conflicts. At the same time, farmers have neither been educated on how to improve irrigation efficiency, nor are they offered any significant incentives to reduce their water usage. Current irrigation efficiency is estimated to be in the range of 50%.

The scenario that has been evaluated for improvement of irrigation methods assumes a transition from the currently used irrigation methods, which mostly involve furrow irrigation, with drip irrigation that is most efficient, for all crop types with the exception of cereals (in the case of garden vegetables or pulses it is assumed that cultivation takes place in greenhouses).

The improvement was scheduled to be implemented gradually in 4 time steps, with time intervals of at least two years between each. Initial implementation was set to begin in 2005, with cost estimated at 0.45 €/m². The maximum feasible penetration was defined by the crop cultivation patterns in each area.

Option results

Figure 1 presents the scheduling for the application of drip irrigation in the municipal department of Agairia under the three scenarios.

Figure 1. Application of drip irrigation in Agairia under the three scenarios

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Effectiveness

Effectiveness to domestic demand coverage presents minor increases under all three scenarios and exhibits a decreasing trend as the demand escalates (Figure 2). The improvement of domestic deficit with respect to each reference scenario is minor, with maximum values ranging from 12% (BAU+Normal) to 35% for the wet periods of the LD+HW scenario (Figure 3). This is due to the reduction of irrigation demand and therefore groundwater abstractions during the low peak months, which results in higher groundwater availability for the prioritised domestic use during the peak summer period.

Figure 2. Percent demand coverage effectiveness of Improvement of Irrigation Methods to Domestic use

Figure 3. Percent Improvement of deficit in Domestic use with respect to the reference scenarios

Figure 4. Percent demand coverage effectiveness of Improvement of Irrigation Methods to Irrigation use

Improvement in irrigation demand coverage is of course very important, reaching a maximum of 90% in terms of effectiveness and of approximately 65% in terms of relative deficit improvement (Figure 4 and Figure 5). However, it should be emphasised that even after irrigation method improvements, irrigation demand is not fully met. Additionally, irrigation deficit improvement is much lower in cases of drought, when available supply is low and a higher priority is given to domestic uses.

Figure 5. Percent Improvement of deficit in Irrigation use
with respect to the reference scenarios

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Direct and Environmental Costs

Direct cost increases are relatively low, ranging from 5% under normal (average) conditions to 5.6 % under a high wet frequency (Figure 6). The small increase is due to the increase of two cost components:

Capital costs, which are associated with the provision of subsidies to farmers for the implementation of the option;
Increase of operating costs, due to the marginal increase of domestic water consumption during the peak summer months.

Figure 6. Total direct cost difference of the Improvement of Irrigation Methods option
under the three scenarios (Present Value – Million €)

The total environmental cost does not differ much after the implementation of the option, presenting only a marginal decrease. As previously stated, since both domestic and irrigation demands are not fully met, all available resources are exploited; thus environmental costs associated with groundwater abstraction remain constant (Figure 7).

Figure 7. Total environmental cost difference of the Improvement of Irrigation Methods
option under the three scenarios (Present Value – Million €)

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